In color image forming devices, image formation is generally carried out by forming color toner images by sequentially superposing toner images of each color on an intermediate transfer belt and then transferring the color toner image onto recording paper; in such image forming devices, the recording paper is transported from a paper feeding unit to a nip between the intermediate transfer belt and a secondary transfer roller, via a paper transport path, then after transfer of the color toner image to the recording paper, the latter is sent via the paper transport path to a fixing unit, and following color toner image fixation, the recording paper is output to a paper output tray via a paper output path.
In an image forming device where the paper output tray is disposed on the upper side of the chassis of the image forming device, and the paper feeding unit is arranged on the lower side of the chassis of the image forming device, the paper transport path takes a substantially vertical form; herein, a guide member is provided in the paper transport path for guiding the recording paper passing through a nip between the intermediate transfer belt and the secondary transfer roller towards the fixing unit.
When a paper jam occurs, the paper jam is handled by opening a lateral cover provided in the chassis of the image forming device to expose thereby the paper transport path (herein, since the secondary transfer roller is provided on the side of the lateral cover, the intermediate transfer belt (in particular, the nip thereof) becomes exposed when the lateral cover is opened). Thus, when the intermediate transfer belt is exposed for handling a paper jam, the user may inadvertently touch the intermediate transfer belt, which might result in faulty imaging.
There are also image forming devices where an openable/closable drum shutter is provided in the vicinity of the photosensitive drum, such that when the lateral cover is closed, the drum shutter is withdrawn, upstream in the paper transport direction from the photosensitive drum, and when the lateral cover is closed, the drum shutter is positioned opposite the photosensitive drum so as to cover the latter.
In conventional image forming devices, when the lateral cover is opened, the photosensitive drum, which is the image carrier, is protected by the drum shutter, while when the lateral cover is closed, the drum shutter is positioned further upstream in the paper transport direction than the photosensitive drum, the role of the drum shutter being to guide the recording paper being transported along the paper transport path in the nip between the photosensitive drum and the transfer roller; however, this is problematic in that an additional mechanism (member) must be provided for separating from the photosensitive drum the recording paper passing through the nip, which increases the number of parts and the like.
In conventional image forming devices, furthermore, the mechanism for moving the drum shutter in response to the opening /closing of the lateral cover is a complex one, and moreover, exposure of the intermediate transfer belt is not prevented when the lateral cover is opened.
In light of the above problems of the prior art, it is an object of the present invention to provide an image forming device having a simple constitution that allows for protecting an intermediate transfer belt when a lateral cover is opened, and that allows for easy separating of the recording paper passing through the nip between the intermediate transfer belt and a secondary transfer belt, when the lateral cover is closed.